Reaction Kinetics, Mechanisms and Catalysis最新文献

Heterogeneous photocatalytic degradation behavior of cationic methylene blue (MB), rhodamine B (RhB), and auramine O (AO) dyes in their ternary aqueous solution, as a model of multicomponent mixture closely imitating a real wastewater, was investigated in great detail. In this study, 100 nm anatase TiO₂ nanoparticles irradiated using 365 nm light were utilized to generate reactive oxygen species capable of oxidizing and degrading unselectively the dyes into small fragments of organic compounds. The underlying kinetics and mechanism of photocatalytic degradation of the dyes were elucidated based on the Langmuir–Hinshelwood kinetic, Weber–Morris intraparticle diffusion, and Smoluchowski diffusion-limited reaction models. The simultaneous photocatalytic degradation of the dyes in their ternary mixture at different irradiation times, catalyst dosages, initial concentrations, pHs of medium, and molarity ratios clearly suggested the dominance of MB in the photocatalytic degradation process due to its faster diffusion over RhB and AO. Increasing temperature or adding a small amount of hydrogen peroxide further highlighted the advantage of MB in the photocatalytic degradation. Overall results revealed a general concept that the molecular structure, especially planarity and electron donating power of attached groups, plays an important role in controlling diffusion dynamics, immobilization, and efficiency of photocatalytic degradation of dyes in multicomponent wastewater.

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This study adopted acid treatment of palm petioles for preparing (APP), which reached notably the whole removal ratio of 99% (60 min) of methylene blue (150 mg/L) and can still maintain good performance after 5 cycles. The adsorbents were analyzed using SEM, FTIR, pH_PZC, and SSA estimation by methylene blue adsorption. The modification of the rough palm petiole with phosphoric acid enables the APP to enhance the intensity of MB adsorption from wastewater. With high R² and the lowest RMSE, the pseudo-second-order model is the most suitable model that describes MB adsorption on APP. There is an intraparticle diffusion, which occurs with the pseudo-second-order. pH has a great effect on MB removal. MB adsorption process was found to be spontaneous and the exothermic. Langmuir model gives very satisfactory results with value of correlation coefficient > 0.93, and the lowest values of RMSE, and saturated monolayers with values of quantities adsorbed close to experimental values. The progressive elimination percentages of the MB on APP were from 95.03% to 41.87% from the first cycle to the fifth cycle of adsorption–desorption. Obtained results have shown that APP is a very promoting adsorbent in the field of wastewater treatment.

A solvent-free metal–organic framework (MOF) [Cu₃(CN)₃(dtb)]_n (1) was hydrothermally constructed depending on 4,4′-di(4H-1,2,4-triazol-4-yl)-1,1′-biphenyl (dtb) and structural characterization was carried out through single crystal X-ray diffraction analysis. Compound 1 reveals an interpenetrated three-dimensional (3D) framework architecture by Cu6(CN)6 rings and dtb ligands, resulting in a fascinating configuration. 1 displays very high thermal stability with the thermal decomposition temperature up to 301 °C and the research on non-isothermal kinetics was conducted at different heating rates through adopting Kissinger’s and Ozawa-Doyle’s methods. Remarkably, the kinetic triplets (the apparent activation energy E_a, the preexponential factor logA and the mechanism function ƒ(α)) and the related thermodynamic parameters (the Gibbs energy of activation ∆G^≠, the enthalpy of activation ∆H^≠ and the entropy of activation ∆S^≠) are discussed and calculated in detail.

Graphical abstract

A solvent-free 3D MOF based on 4,4′-di(4H-1,2,4-triazol-4-yl)-1,1′-biphenyl presents high thermal stability and its thermal decomposition kinetics was investigated.

In a previous work, a cellulose paper film containing a nanocomposite charge (TiO₂/5%-curcumin) was developed and used in the photocatalytic degradation of methylene blue (MB), an organic dye, on a tubular reactor with trickling and circular flow under UV irradiation light. The effect of three main operational parameters on the photocatalytic degradation of MB was studied: the mass of TiO₂/5% Curcumin material deposited on the cellulose paper, the initial concentration of the pollutant (MB) and the intensity of UV irradiation light. The obtained results show that by working under operating conditions of mass of deposited material (14 mg), initial pollutant concentration (10 ppm) and intensity of UV irradiation light (3.76 w/cm²), approximately 85% of MB was removed after 220 min of irradiation. To help guide future experimental efforts, the present work proposes a data augmenting self-attention network (DASAN) for the prediction of the photocatalytic degradation efficiency from a set of experimental parameters. The suggested ensemble combines base models for data augmentation and a meta model incorporating a self-attention mechanism for the prediction. The model is trained using the obtained experimental data of operating conditions (mass of material, initial pollutant concentration and intensity of UV irradiation light). The base models achieved excellent fits to the data and the meta model attained a mean squared error of 0.0055 through five-fold cross-validation, predicting optimal degradation efficiencies of 86–90% for experimental values of 20–22 mg the catalyst charge, 11–15 ppm for the initial pollutant concentration and 4.4–5.7 w/cm² for the intensity of UV irradiation light.

In this work, a series of bimetallic nano-oxide ZrO₂–CeO₂ xerogel adsorbent with different Ce/Zr molar ratio (0.1, 0.2, 0.3 and 0.5) were prepared in one step via sol–gel method in order to obtain the highest-performing composition for fluoride removal from drinking water. BET, SEM, EDX, TEM, FTIR spectroscopy, and XRD techniques were performed to characterize the solids before and after fluoride adsorption. The selected material exhibits a high surface area (S_BET = 255 m² g⁻¹) and a large porosity (V_P = 0.30 cm³ g⁻¹). FTIR spectroscopy demonstrated the significant role played by the adjunct sulfate anion and superficial hydroxyl groups in the defluorination process. Thermodynamic study confirms that the sorption is spontaneous and endothermic. Our adsorbent's behavior for the removal of fluoride is described by the Freundlich isotherm model. The pseudo-second order kinetic model represents the adsorption kinetic process. Less than 1 min, 100% of fluoride removal is reached in a wide pH range (2–8). The results of this study were effectively applied to natural drinking water in Tunisia. The development of innovative water treatment technology can be effectively advanced by using our multifunctional nano-oxide.

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This study aims to investigate the atmospheric water sorption kinetics of a CaCl₂ salt-impregnated sorbent derived from waste sugarcane biomass under real-time semi-arid to semi-humid conditions. The samples prepared by impregnating highly porous activated carbon prepared from waste sugarcane bagasse in different salt concentrations of CaCl₂ was initially screened based on its water uptake and sorption kinetics. Subsequently, the screened sorbent underwent further characterization to assess its textural properties, surface morphology, thermal stability, functional groups, and density. Under low relative humidity (RH) conditions ranging from 30 to 50%, the sorbent exhibited commendable water uptake ranging between 0.71 and 0.95 g/g, coupled with rapid adsorption and desorption kinetics. The sorbent also demonstrated operational stability over 10 adsorption–desorption cycles. The experimental water uptake data was also fitted using the Linear Driving Force (LDF) model to determine the sorption rate constant and resulted in a very good agreement with the model. Furthermore, at 60 °C, more than 80% desorption was attained, indicating the feasibility of solar-assisted operation. This study highlights the potential of sorbents derived from waste biomass for sustainable AWH applications.